A Review of Patents and Innovative Biopolymer-Based Hydrogels

Abstract

Biopolymers represent a great resource for the development and utilization of new functional materials due to their particular advantages such as biocompatibility, biodegradability and non-toxicity. "Intelligent gels" sensitive to different stimuli (temperature, pH, ionic strength) have different applications in many industries (e.g., pharmacy, biomedicine, food). This review summarizes the research efforts presented in the patent and non-patent literature. A discussion was conducted regarding biopolymer-based hydrogels such as natural proteins (i.e., fibrin, silk fibroin, collagen, keratin, gelatin) and polysaccharides (i.e., chitosan, hyaluronic acid, cellulose, carrageenan, alginate). In this analysis, the latest advances in the modification and characterization of advanced biopolymeric formulations and their state-of-the-art administration in drug delivery, wound healing, tissue engineering and regenerative medicine were addressed.

Keywords: alginate; carrageenan; cellulose; chitosan; collagen; fibrin; gelatin; hyaluronic acid; keratin; silk fibroin.

Figure 1

Numbers of patent documents (patent applications, granted patents) of biopolymer-based hydrogels from 1915 to May 2023. Data were obtained using the Espacenet database [13].

Figure 2

Schematic representation of (A) the synthetic and biosynthetic polymers discussed, evidencing their available functionalities for interacting with keratin; (B) the elastomers and thermoset polymers discussed, evidencing their generalized structures and available functionalities for interacting with keratin; (C) the natural polymers discussed (carbohydrates and proteins), evidencing their generalized structures and available functionalities for interacting with keratin. Reprinted from ref. [64] under open access creative common CC-BY license.

Figure 3

(a) Schematic representation of preparation of GL-PC porous hydrogels for cultivated meat production. (b) Digital photograph images of GL-PC hydrogels after freeze-drying. (c) Digital photograph images of the stability of GL-PC hydrogels in PBS (pH 7.4) at 37 °C. (d) Digital photographs of GL-PC hydrogels before and after compression. (e) Compressive analysis of GL-PC hydrogels. Reprinted from ref. [88] under open access creative common CC-BY license.

Figure 4

(A) Prospective binding mechanisms for Cs(I) and Sr(II) sorption onto ALG-PEI and APO-PEI sorbents. (B) SEM photos for shape and size evaluation of sorbent particles. (C) SEM observation (left panels) and semi-quantitative EDX analysis (right panels) of ALG-PEI after Sr(II) sorption (a) Cs(I) sorption (b); APO-PEI after Sr(II) sorption (c); and Cs(I) sorption (d). Reprinted from ref. [146] under open access creative common CC-BY license.

Figure 5

(A) Schematic illustration for the formation of CMC/PA hydrogels and the inverted vial test. (B) Equilibrium degree of swelling of the hydrogels at different CMC/PA molar ratios. (C) Cell viability of normal human dermal fibroblasts exposed to hydrogel extracts (500/250/125/62, 5 µg/mL) for 24 h. Experiments were conducted in triplicate, and treated cell viability was expressed as percentage of control cells’ viability. Graphical data were expressed as means ± standard error of the mean. Reprinted from ref. [187] under open access creative common CC-BY license.

Figure 6

(A) Preparation of NaOH/urea-treated TEMPO-oxidized cellulose using a two-step process. (B) Dispersion states of (a) pristine cellulose; (b) NaOH/urea-treated cellulose; (c) direct TEMPO-oxidized cellulose; and (d) NaOH/urea-treated TEMPO-oxidized cellulose. (C) Optical microphotographs of (a) pristine cellulose; (b) NaOH/urea-treated cellulose; (c) direct TEMPO-oxidized cellulose; and (d) NaOH/urea-treated TEMPO-oxidized cellulose. (Inset in (d) is the TEM image of NaOH/urea-treated TEMPO-oxidized cellulose.) Reprinted from ref. [188] under open access creative common CC-BY license.